Specifications

10-29
Cisco IGX 8400 Series Provisioning Guide, Release 9.3.3 and Later Releases
OL-1166-04
Chapter 10 Cisco IGX 8400 Series IP Service
IP Service—Functional Overview
Figure 10-14 Using MPLS to Build VPNs
One strength of MPLS is that providers can use the same infrastructure to support many VPNs and do
not need to build separate networks for each customer. VPNs loosely correspond to “subnets” of the
provider network.
This solution builds IP VPN capabilities into the network itself, so providers can configure a single
network for all subscribers that delivers private IP network services such as intranets and extranets
without complex management, tunnels, or VC meshes. Application-aware QoS makes it possible to
apply customer-specific business policies to each VPN. Adding QoS services to MPLS-based VPNs
works seamlessly; the provider Edge LSR assigns correct priorities for each application within a VPN.
MPLS-enabled IP VPN networks are easier to integrate with IP-based customer networks. Subscribers
can seamlessly interconnect with a provider service without changing their intranet applications,
because these networks have application awareness built in, for privacy, QoS, and any-to-any
networking. Customers can even transparently use their private IP addresses without NAT.
The same infrastructure can support many VPNs for many customers, removing the burden of separately
engineering a new network for each customer, as with overlay VPNs.
It is also much easier to perform adds, moves, and changes. If a company wants to add a new site to a
VPN, the service provider only has to tell the CPE router how to reach the network, and configure the
LSR to recognize VPN membership of the CPE. BGP updates all VPN members automatically.
This scenario is easier, faster, and less expensive than building a new point-to-point VC mesh for each
new site. Adding a new site to an overlay VPN entails updating the traffic matrix, provisioning
point-to-point VCs from the new site to all existing sites, updating OSPF design for every site, and
reconfiguring each CPE for the new topology.
Edge LSR
PE
CE
Edge LSR
PE
Customer B
10.1.1
VPN 354
CE CE
Customer A
10.2.1
VPN 15
MPLS network
Customer A
10.1.1
VPN 15
(15) 10.1.1
Customer A
10.3.1
VPN 15
Customer B
10.2.1
VPN 354
Controlled route distribution
(354) 10.1.1
(354) 10.2.1
(15) 10.3.1
CE
CE
(15) 10.2.1
25098
Edge LSR
PE
Forwarding examples
IN
OUT
(15) 10.2.1
(354) 10.2.1
(15) 10.1.1
(15) 10.3.1
(354) 10.1.1